Reason I bring this up is because there's a discussion at Pistol-Forum.com on how to cycle duty ammo, and the constant re-chambering came up. Here's a story from that thread that I think may influence people to be more careful:
THE FOLLOWING TRAINING ADVISORY WAS FORWARDED FROM GWINETT COUNTY POLICE DEPARTMENT - LAWRENCEVILLE, GAOf note about the above advisory is that if you do use a trigger lock, do not use it if the weapon is loaded. That's bad.
In September of this year a GCPD officer was involved in a situation which quickly became a use of deadly force incident. When the officer made the decision to use deadly force, the chambered round in his duty pistol did not fire. Fortunately, the officer used good tactics, remembered his training and cleared the malfunction, successfully ending the encounter.
The misfired round, which had a full firing pin strike, was collected and was later sent to the manufacturer for analysis. Their analysis showed the following: "...the cause of the misfire was determined to be from the primer mix being knocked out of the primer when the round was cycled through the firearm multiple times". We also sent an additional 2,000 rounds of the Winchester 9mm duty ammunition to the manufacturer. All 2,000 rounds were successfully fired.
In discussions with the officer, we discovered that since he has small children at home, he unloads his duty weapon daily. His routine is to eject the chambered round to store the weapon. Prior to returning to duty he chambers the top round in his primary magazine, then takes the previously ejected round and puts in back in the magazine. Those two rounds were repeatedly cycled and had been since duty ammunition was issued in February or March of 2011, resulting in as many as 100 chambering and extracting cycles. This caused an internal failure of the primer, not discernible by external inspection.
This advisory is to inform all sworn personnel that repeated cycling of duty rounds is to be avoided. As a reminder, when loading the weapon, load from the magazine and do not drop the round directly into the chamber. If an officer's only method of safe home storage is to unload the weapon, the Firearms Training Unit suggests that you unload an entire magazine and rotate those rounds. In addition, you should also rotate through all 3 duty magazines, so that all 52 duty rounds are cycled, not just a few rounds. A more practical method of home storage is probably to use a trigger lock or a locked storage box.
The primer compound separation is a risk of repeatedly chambering the same round. The more common issue is bullet setback, which increases the chamber pressures often resulting in more negative effects.
In addition to following the guidance provided above of constantly rotating duty ammunition that is removed during the unloading/reloading of the weapon, training ammunition utilized during firearm sustainment and weapon manipulation drills, should also be discarded if it has been inserted into the chamber more than twice. This practice lessens the likelihood of a failure to fire or more catastrophic results.
It's not just the primer that's effected by re-chambering; the seating depth is also effected, which is more critical in handgun cartridges because small movements of a thousandth of an inch can be all it takes to overpressure the load when fired, blowing your gun to smithereens. This is even more so with +P loads that are already running hot. If you're as safety minded as I am, it's not worth the $.50 in savings to keep reusing that Gold Dot, so stick in a range-fodder box after you eject it.